Patent application PCT FR99/00737 proposes a zirconium-based alloy also containing, by weight, apart from unavoidable impurities, from 0.03 to 0.25% in total of iron, on the one hand, and of at least one of the elements of the group constituted by chromium and vanadium, on the other hand, having from 0.8 to 1.3% of niobium, less than 2000 ppm of tin, from 500 to 2000 ppm of oxygen, less than 100 ppm of carbon, from 5 to 35 ppm of sulphur and less than 50 ppm of silicon, the ratio of the iron content, on the one hand, to the chromium or vanadium content, on the other hand, being from 0.5 to 30.
The invention is based on observations made by the inventors in the course of a systematic study of the intermetallic phases and the crystallographic forms of those phases which appear when the relative contents of iron and niobium are varied while the contents of tin, sulphur and oxygen are described in the application mentioned above. It is also based on the observation, made experimentally, that the nature and the crystallographic form of the intermetallic phases containing zirconium, iron and niobium have a major influence on corrosion resistance in various environments.
In particular, it has been found that the presence of compounds having a crystalline structure with a face-centered cubic lattice, obtained owing to a proportion of iron relative to niobium sufficient to result in the presence of (Zr Nb)4Fe2, at the expense of the compound Zr (Nb, Fe)2 having a hexagonal lattice, and of the phase βNb, which predominate at the high Nb/Fe ratios, substantially improves corrosion in a medium having a high lithium content, such as that which exists at the beginning of an operating cycle of some pressurized-water reactors. On the other hand, the presence of the phase having a face-centered cubic lattice in too large a quantity slightly impairs corrosion resistance in an aqueous medium.